net: ipa: no more global filtering starting with IPA v5.0

IPA v5.0 eliminates the global filter table entry.  As a result,
there is no need to shift the filtered endpoint bitmap when it is
written to IPA local memory.

Update comments to explain this.  Also delete a redundant block of
comments above the function.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>